Piston for internal-combustion engines.



n. 1. CAMPBELL. HSTON FOR LNTERNAL COMBUSTION ENGINES,

APPLICATION FILIiD JAN.22. I916.

Patented ay 7,1918.

mthltlhhm JAMES UAMPEEJLL, or MUSKEGON HEIGHTS, MICHIGAN.

rrsrorr Filth, WWJEWAL-COMBU$TION ENGINES.

near-nae.

To all whom it may concern." Bait known thatl, DONALD Janus Catar- BELL, a citizen of the United htates ct America, residing at Muskegon Heights, in the county of Muskegon and State of Michigan, have invented certain new and useful Improvements in Pistons for internal-Combustion Engines; and l do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same,

My invention relates to improvements in so-called, trunk pistons for internal combustion engines, and more particularly in con structing such pistons from, two metals, as willbe hereinafter more fully described and particularly pointed out in the claims, reiterence being had to the'accompanying drawing, in which:

Figural, shows a side elevation ot my improved form of piston, and, Fig. 2, shows the same in vertical section on the line 22, of Fig. l.

Like indices refer to like parts in both figures.

In present practice, in the construction of the so called, high speed and high compression internal combustion engines, it has been found very advantageous to construct the pistons of such engines just as light, in weight, as the various coeflicients of strength of the metal, from which they may be made, will permit, having due regard as to the stress, strains and temperatures to which such pistons are to be subjected.

In conformity with the foregoing stated practice, there have been used, pistons made from various alloys of aluminum, which have attained varying degrees or success and failure. It has been found in practice, that such aluminum alloy pistons have given considerable trouble, in t at, any available alloy of aluminum that has thus far been produced has not, under the conditions of the extremel high temperatures and the shock and stream of the blow of the explosions to which such istons must, of necessity, be subjected un or working conditions, proven capable of standing up as they. should under Specification of Letters Patent.

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continuous heavy load, except when such pistons are made with comparativel very heavy walls, articularlyin the hea s, and even then, i such pistons are over three inches in diameter, the heads require deep, heavy bracing ribs. in the designing of pietons to be made from aluminum alloys, it

has been found necessary to make the heads thereot very much thicker and to more thoroughly rib and brace the, same to enable them to withstand the temperature and shock of the explosions. These conditions make it necessary to providealuminum alloy pistons with comparatively very heavy heads and numerous deep ribs, and thus the single,

desirable feature of aluminum alloy pistons,

namely; lightness, is to a very material eatent negatived by/this thickness of wall and numerous ribs. Another very material point militating against the satisfactory performance of aluminum alloy pistons 18 the high thermal conductivity of such alloys, as compared with iron or steel. Thus, the head of an aluminum alloy piston, being subjected to the extremely high temperature of the explosions, possesses the capacity of absorbing and conveying to the skirt or barrel of such pistons, a much greater quantity of heat, than would a steel or iron piston, under like temperature and working conditions. lfhis property of hi h thermal conductivity is most undesirab e in a piston for internal combustion engines, because, so much more heat will be comreyed to the oilfilms on the piston and cylinder walls and the bearings of the piston pin that the proper and required lubrication of these. parts is rendered much 'more 'thannormally diihcult to efiect and maintain because of the much more rapid carbonization of the oil films. An other condition which is claimed to exist in internal combustion engines .in which aluminum alloy istons are used, and particularly in which t e so called, splash system of lubrication is used, is: that because of the greater heat conductivity of aluminum alloy pistons, as compared with iron 'or steel pistons, the oil in the supply reservoir in the crank case is raised to a much higher temperature than it is when iron or steel pistons are used, and thus such oil is rendered less efiicient in lubricating power, and becomes more quickly burned or carbonized and its or steel.

.irpn plstons., andlthus it is'lmu'ch'. more difficult, {if not quit-eimpossible, to produce a quiet, efficient Working/piston, under the varyingconditionsof speed and load required,. froni. an aluminum alloy, than to produce such a piston from iron or steel.

" Finally, the melting point of aluminum is practically only one half that of cast iron (Aluminum 6259 (3., cast iron -12'20 G, and steel 14:00. (3;, Roberts-Austen, authority.) i v Having thus pointed out the comparatively well known advantages and disadvantages of pistons as now constructed, I will now proceed to describe and explain my present invention.

By the utilization of my present invention I amable to retain all of the advantages of strength, resistance tooverheating and low coeflicie-nt of expansion and high melting point inherent in the full cast iron or steel piston, while b the same structure I gain the advantage 0 reduction of weight of aluminum alloy pistons," while at the duces a piston which site factors of strengt tion, low coefiicients of thermal conductivity same time I avoid the very fra ile nature, high thermal conductivity and igh coeffi-.

' cient ofexpansion and low melting point of the same. By using cast iron or an equ1va-- lent metal for the head portion the same can-be made with a very thin wall and few strengthening ribs and such ahead ortion. .in combination with a thin 'wa led aluminum alloy skirt or barrel portion, proplos'sesses all the requiresistance to distorandexpansion and high melting oint of the part which is directly expose to the; extreme heat and the shock ofthe explosion, while at the same time such .a piston is substantially, if not fully, as light in weight as a full aluminum alloy piston can be made which woud withstand the strains and 'heat to which it would be subjected under working conditions. v

Referring to the accompanying drawing,

Fig. 1, it'will be noted, that theexternal appearanceof my improved form of piston A the same as the ordinary usual construcskirt or barrel portion 2, and

tion of trunk piston; referring to Fig. 2, 1, is the head of the piston, which is to be produced, preferably, from cast iron, the surfaces of which, from the point (a continuously, longitudinally and circum erentially, down to the point ((2), are to be thorbughly cleaned, preferably by machining, before the barrel or skirt portion.2,. (which is to be produced, preferably, from a light weight aluminum alloy)'-,-'is-'joined to the head portion 1. I prefer to accomplish the joining ofthe two said parts by casting "the'skirt' or barrel portion ntothe head portion. This may be easily done by fixing the head 1, on a formed casting core, then placing the said core together. with :the; part- 1, attached theretm'into asuitably prepared mold and casting the skirt or barrel portion 2', onto the head 1. This method is entirelypracticable,

since the temperature of the melted aluminum alloy is far below the melting point ofthq material from which the head portion 1 is to be made;- It'will be noted that the projecting flange 1?, of the head l will,

roove in the by the interlocking of this groove and flange the head and skirt-will be held insepara curely together.

In the construction as shown in the draw ing, to make special provision against rupture of the skirt 2, where it, in cooling, shrinks onto the head 1, I have provided at the points (0) and (d), a compressible packing or gasket, preferably .of' asbestos tape, but this provision is not absolutely necessary, for-I have found in practice that by at the time'of casting, form a heating the head 1, to as high a tempera-.

ture asthe core to which it is attached will stand, without crumbling or breaking up, the normal shrinkage of the skirt 2, and the head 1, in cooling, will bejust right to form a firm stable joint between these two parts,

ly and sewithout putting undue strain on the skirt or barrel portion 2. I have also thought it expedient to provide, in the piston pin bosses, a lining or bushing 3, of steel or any. suitable bearing metal. Said linings may be formed from tubes, with a portion-as at 4:,

removed throughout, their entire length. This opening permits of compression of the linings 3, as the metal of the-bosses shrink in cooling. These linings. 3, are also to be fixedonto the casting core, and thus, when the skirt or barrel 2,.is cast, become rigidly fixed into the bosses ofthe same. These linings 3, as well as, the or gaskets (a) and ((1), may ispensed with, without departing, from the essential features or spirit of .-my invention. Y

The required maehmin'gnt my: improved construction of piston -may. -be, performedin the same manner-as that of, he standard form of trunk pistons. I-desire to call, at

a kingstention to the fact, that in my improved construction of piston, only so much heat can be transmitted to the skirt or barrel portion 2, as would normally be transmitted to the skirt' or barrel of a full steel or iron piston, since the absorption of heat from the explosions is limited to the amount of heat which can be absorbed and transmitted by the steel or iron head, and even this transmission will be abnormally retardedon account of the fact, that in operation oil will work into the joint between the head 1, and skirt 2, and act as a partial heat insulation, the result being that, the aluminum alloy skirt or barrel 2, of my improved form of piston, will under working conditions, remain at a'much lower temperature than it would be possible for the skirt or barrel of a full aluminum alloy piston to work at, and as accurately as it has been possible for me to determine, the aluminum alloy skirt incense or barrel of my improved form of piston remains at substantially the same temperature, or a trifle lower, than would the skirt or barrel of a full steel or cast iron piston, working under like conditions.

It will be further noted, that because of the reduction of the quantity of heat trans- 2, the expansion of this aluminum alloy skirt will be very materially reduced, as compared with the expansion ofthe skirt of a full aluminum alloy piston, and thus, at least a material part, of one of the great disadvantages of an aluminum alloy piston will be quite materially reduced. I

Another point to be observed is: that by my improved construction I have so ar-' ranged the arts, so that, the metal of the highest coefficient of expansion is subjected to the least influence of the-extreme heat of the combustion chamber, and at the same time, should any abnormal condition arise by which this aluminum alloy skirt 2,

should be caused to unduly expand'trom the} effect of heat, either frictiona-lly generated or transmitted, said skirt 2, is free ,to ex pand away from the iron or steel head 1, at. their point of engagement, and thus neither the skirt nor head would be distorted or broken by such excessive expansion.

1 do not Wish to be understood as limiting my invention to the exact specific details of construction which l have herein shown and described, since, variations in the details of construction may be had without departing from the essential purpose or spirit of my invention. Nor do I, limit my invention to the use of a cast iron head, or any articular' alloy of aluminum from which t e skirt is to be made, since, the heads may be made from cast iron, steel or nickel, or alloys 015 any twoor more of such metals, and formed,

by stamping, torgihg or casting, and the characteristics of high melting point, high resistance to deflecting strains, fire erosion and mechanical abrasion, with a low coefficient of expansion and thermal conductivity, and to have-fixed thereto, a skirt or barrel portion to be made from a metal possessing one essential physical property, namely, relative lightness, as compared with the metal from which the head is made.

ll claim:

1. A piston comprising a head portion and a skirt portion inseparably joined together in operative relation by a groove and flange connection. A i

2. A piston of the class described consisting of, a head portion made from a metal, the physical properties and characteristics of which are, high melting point, high resistance to deflecting stresses and relatively low thermal conductivity and. expansion,

. tion.

3. A piston of the class described consisting of, a head portion made from amet-al, the

physical. properties and characteristics ich are, high melting point, high re-' sistance to deflecting stresses and relatively low thermal conductivity and expansion,

and a skirt or barrelportion made from a metal, the principal physical property of which is lightness a's compared with the metal of the said head, said parts being innamely, oii'tensile strength, resistance to de fleeting strains, coefficients-ot thermal conductivity, expansion, melting point and relative weight, said parts being inseparably joined by casting the part made from the metal of the lower other part 5. A piston otthe class described comprising a head portion of cast iron, and a skirt melting point onto the separably joined together in operative reportion of aluminum alloy, said two portions being inseparably joined by means ofinterlocking portions of one member engaging corresponding interlocking portions on the other member.

6. A piston of the class described comprising, a cast iron head ortion having an external circumferentia groove, an aluminum alloy skirt portion inseparably joined to said head portion by being cast onto the 10 same so that an internal projecting flange of said skirt. portion engages the said groove of said head portion.

In testimony whereof- I hereunto aflix my signature to-the foregoing specifications and 15 claims.

DONALD JAMES CAMPBELL. 

